Wireless communication systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include code-division multiple access (CDMA) systems, time-division multiple access (TDMA) systems, frequency-division multiple access (FDMA) systems, and orthogonal frequency-division multiple access (OFDMA) systems.
By way of example, a wireless multiple-access communication system may include a number of base stations, each simultaneously supporting communication for multiple communication devices, otherwise known as user equipments (UEs). A base station may communicate with UEs on downlink channels (e.g., for transmissions from a base station to a UE) and uplink channels (e.g., for transmissions from a UE to a base station).
Some modes of communication may enable communications between a base station and a UE over an unlicensed radio frequency spectrum band, or over different radio frequency spectrum bands (e.g., a licensed radio frequency spectrum band and/or an unlicensed radio frequency spectrum band) of a cellular network. With increasing data traffic in cellular networks that use a licensed radio frequency spectrum band, offloading of at least some data traffic to an unlicensed radio frequency spectrum band may provide a cellular operator with opportunities for enhanced data transmission capacity.
Prior to gaining access to, and communicating over, an unlicensed radio frequency spectrum band, a base station or UE may perform a listen before talk (LBT) procedure to contend for access to the unlicensed radio frequency spectrum band. An LBT procedure may include performing a clear channel assessment (CCA) procedure to determine whether a channel of the unlicensed radio frequency spectrum band is available. When it is determined that the channel of the unlicensed radio frequency spectrum band is not available (e.g., because another apparatus is already using the channel of the unlicensed radio frequency spectrum band), a CCA procedure may be performed for the channel again at a later time.
In environments in which a base station or UE may be starved of access to a channel of an unlicensed radio frequency spectrum band due to Wi-Fi activity, an extended CCA procedure may be employed to increase the likelihood that the base station or UE will successfully contend for access to the channel of the unlicensed radio frequency spectrum band. A similar procedure is not currently available to Wi-Fi nodes (e.g., Wi-Fi access points and/or Wi-Fi stations).